Restoration of Hip Kinematics After Arthroscopy for Femoroacetabular Impingement Syndrome: A 1-Year Evaluation of Gait and Stair Performance

Background: Femoroacetabular impingement syndrome (FAIS) is common in athletes, and the effect of biomechanics and biomechanical alterations after hip arthroscopy continues to be investigated. This study aimed to assess the effect of hip arthroscopy on biomechanical function in patients with FAIS during gait, stair ascent, and stair descent. Hypothesis: Patients with FAIS would exhibit decreased motion preoperatively compared with contralateral asymptomatic hips, but these differences would be corrected postoperatively and these changes would correlate to improvements in patient-reported outcome measures (PROMs). Study Design: Case series; Level of evidence, 4. Methods: Ten patients undergoing hip arthroscopy for FAIS were included and completed PROMs as well as kinematic assessment at baseline and 1 year postoperatively. 3D motion tracking was performed using a 10-camera system while patients performed gait, stair ascent, and stair descent. Joint kinematic parameters were calculated in the sagittal, coronal, and transverse planes for the symptomatic and contralateral side. Peak and valley angles for each joint during each task were compared between limbs using linear mixed-effects models. Significant changes in kinematics were correlated to PROMs. Results: Preoperatively, the symptomatic hip demonstrated significant deficits in gait and stair ascent compared with the contralateral hip. During gait, hip kinematics increased compared with before surgery with respect to flexion (+7.7°± 7.3°), abduction (+2.4°± 3.2°), and external rotation (ER) (+3.0°± 4.9°) ( P < .01). During stair ascent, hip abduction (+2.8°± 1.7°) and ER (+2.8°± 5.7°) were significantly increased ( P < .01). During stair descent, hip flexion (+2.5°± 6.4°), extension (+3.9°± 8.3°), abduction (+2.3°± 2.6°), and ER (+4.8°± 4.3°) were significantly increased ( P < .01). Significant improvements were seen in patient-reported outcomes, but these did not correlate to hip kinematics. Conclusion: Hip arthroscopy for FAIS improved hip flexion, abduction, and ER during dynamic tasks such as gait, stair ascent, and stair descent comparable with the contralateral extremity. Additionally, patients reported significant improvement in function and pain at 1 year postoperatively, but these improvements did not correlate with improvements in hip kinematics.